099 CD4 T cells require CD8 T cells to induce disease in murine alopecia areata

Abstract

Alopecia areata (AA) is a common autoimmune disease characterized by T cell infiltrates centered around the hair follicle resulting clinically in hair loss. Prior studies implicated a role for NKG2D-expressing CD8 T cells in AA pathogenesis. CD4 T cells, however, outnumber CD8 T cells in the peribulbar infiltrate in AA patients, and much less is known about how CD4 T cells may be participating in disease development. We therefore sought to confirm a role for CD4 T cells in AA by use of a recently-described model of murine AA induction. We hypothesized that CD4 T cells alone from in vitro expanded cultures of AA lymph nodes could transfer disease to recipient mice. Adoptive transfer recipients of in vitro expanded CD4 T cells demonstrated hair loss, and CD4 T cell-induced AA mice exhibited the hallmark NKG2D-expressing CD8 cells in the skin and lymph nodes. Interestingly, depletion of CD8 T cells prevented CD4 T cell-mediated induction of AA, indicating that CD8 T cells are necessary for CD4 T cell-induced AA. Our data suggest that CD4 T cells enable CD8 T cells to attack the hair follicle or alternatively make the hair follicle susceptible to immune attack by CD8 T cells. Future work will dissect the CD4 T cell-mediated mechanisms and effector functions that lead to AA.